Health outcomes research is essential for making effective clinical research and practice decisions. Improving patient-reported outcomes, such as Quality of Life (QOL), has the potential to improve health quality and equity, especially for underserved populations, as well as reduce the practice of costly or ineffective treatment. Developing an outcome measure that focuses on the quality of life of Latino populations has a substantial public health impact and is crucial to provide a complete picture of an individual's physical and mental health status. Our prior work yielded the Adolescent Quality of Life-Mental Health Scale (AQOL-MHS), a new Spanish language instrument that focuses on the QOL of adolescents (12-18 years old) with mental health problems. The AQOL-MHS was developed in Spanish with Puerto Rican adolescents living on the island and has produced promising results. This renewal application extends our work in three significant areas: It expands the analyses of longitudinal data for the AQOL-MHS, focuses attention on the longitudinal utility of the measure, and examines barriers to its clinical applicability. The proposed aims will: 1) assess the ability of the AQOL- MHS to detect change in quality of life over time using innovative psychometric models of change and 2) consider refinements to the AQOL-MHS that improve its sensitivity to change. To achieve these aims we will adapt psychometric methodology from diary research and ambulatory assessment to the field of QOL research, in order to measure change over the course of treatment and post-treatment using Generalizability Theory. This will be conducted with secondary data analyses. We will then use these results to refine the AQOL-MHS to be sensitive to change and test them in new data collection with an increased sample size of 250 adolescent participants and four waves of data. We will also examine the barriers experienced by mental health providers in utilizing the AQOL-MHS in their practice using a mixed methods design (n=30). This includes exploring new technological solutions to overcome barriers regarding the administration of the AQOL- MHS in clinical settings. We believe that the AQOL-MHS will help integrate research into practice by providing feedback to the provider to improve care, and serve both as a screening tool for further exploration of diagnosis and treatment, as well as function as a mental health QOL assessment instrument to evaluate treatment outcomes.